Method and system for performing re-association due to handover in a wlan mesh network

ABSTRACT

A method and system for performing re-association in a WLAN mesh network are provided. A mobile node transmits authentication request information to an old node via a new node along with a mesh re-association request message for re-association of the mesh network. Upon receiving the mesh re-association request message, the old node performs re-association and authentication according to the mesh re-association request message, and transmits a mesh re-association reply message to the mobile node via the new node.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.11/432,666 filed on May 12, 2006, which claims the benefit of U.S.Provisional Application No. 60/680,044, filed on May 12, 2005, andclaims the benefit of Korean Application No. 10-2006-0036684, filed onApr. 24, 2006, in the Korean Intellectual Property Office, the entiredisclosures of which are hereby incorporated by reference for allpurposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a Wireless Local Area Network(WLAN) mesh network. More particularly, the present invention relates toa method and system for performing re-association due to the movement,such as, handover, of a mesh point in the network.

2. Description of the Related Art

A Local Area Network (LAN)is a set of personal terminals, main frames,and workstations connected to one another with a communication line of300 meters or shorter. A LAN is also a high-speed communication networkconnected so that remotely installed equipment in which currents orradio signals between the personal terminals can be correctly delivered.For example, the equipment in the building of one institution can beefficiently shared by the entire staff. In the past, the wired networksthat directly delivered the electric signals were mainly used ascommunication lines applied to the LAN. Due to the development ofwireless protocols, the wired networks are increasingly replaced withwireless networks that deliver signals using radio waves. The LAN usingthe wireless network is generally called a Wireless Local Area Network(WLAN), or a wireless in-building information communication network,which is based on IEEE 802.11 proposed by the Institute of Electricaland Electronics Engineers (IEEE). The IEEE 802.11-based WLAN has grownat a fast rate in recent years, and is expected to make more rapiddevelopments in the future due to its advantage of convenient networkconnection. As the demands for the high-speed wireless Internet increaserapidly, the existing WLAN system serves as an alternative to theinfrastructure of the high-speed wireless public network.

The WLAN includes a plurality of access points (APs) connected via onedistribution system (DS), and a plurality of stations (STAs) thatreceive services via the APs. Therefore, the AP serves as a bridgebetween terminals and the remainder of the network.

In a WLAN, the STA performs handover to a new AP from which it willnewly receive the service when strength of a signal received from itscurrent AP decreases due to its mobility. Therefore, in order to switchthe service to the new AP, the STA needs authentication andre-association with the new AP. In this case, the STA performs handoverfrom the old AP with which it has been communicating, to the new AP. Thehandover process will be described below with reference to FIG. 1.

FIG. 1 is a signaling diagram schematically illustrating a handoverprocedure due to the movement of an STA in a general WLAN.

Referring to FIG. 1, a procedure is shown in which an STA 100 moves froman old AP 140 to a new AP 130. The STA 100, due to the movement,performs a Probe phase for asking each individual AP its opinion on thepossibility of handover success.

The STA 100 sends a Probe Request message to a plurality of unspecifiedAPs 120 in steps 111 and 115. Upon receiving the Probe Request message,the APs 120 transmit a Probe Response message to the STA 100 in step 113and 117. The phrase “receiving the Probe Request message” means that thecorresponding AP is adjacent to the mobile station (STA), so the AP canbe assumed to be a latent AP. The Probe phase is repeatedly performedfor each individual channel. The process of performing the Probe phaseby changing the channel is shown in steps 115 and 117.

The STA 100 generates a priority list of the APs through the Probephase. AP priorities are determined using strengths of signals receivedfrom the APs, by way of example.

The STA 100 performs an Authentication phase with the latent APsaccording to the priority list in steps 119 and 121. The STA 100 canperform the Authentication phase of requiring delivery of a credentialand other state information from the old AP 140, via the new AP 130.

Next, the STA 100 performs a Re-association phase. The handover can beachieved through the Re-association phase and an Inter-Access PointProtocol (IAPP). Delivery of the state information is performed by theIAPP. The state information commonly refers to information thatfacilitates access to the network and the information includesinformation on a client's position and several accountings.

The STA 100 performs the Re-association phase based on the priorities ofthe latent APs registered in the priority list generated in the Probephase. The STA 100 then transmits a Re-association Request message tothe new AP 130 in step 123. The new AP 130 then performs an IAPPprocedure with the old AP 140 through the other APs in steps 125, 127,129 and 131. Through this procedure, the new AP 130 receives acredential allocated to the mobile station and other state information.

In step 133, the new AP 130 sends a Re-association Response message tothe mobile station in response to the Re-association Request message.

As described above, the conventional handover procedure starts when themobile station sends a Probe Request message, and ends when the mobilestation receives a Re-association Response message. As a result, thehandover procedure suffers from a probe delay, an authentication delay,and a re-association delay. The probe delay occurs in the Probe phase,the authentication delay occurs in the Authentication phase, and there-association delay occurs in the Re-association phase.

First, the probe delay occurs while the STA 100 transmits a ProbeRequest message and waits for a response thereto for each individual APin each channel. The time for which the mobile station waits for theresponse in a particular channel after transmitting the Probe Requestmessage is called a probe-wait delay. This is determined based on a timedifference with the next transmitted Probe Request message. As a result,the traffic in the channels and timing of the Probe Response message mayaffect the probe-wait time.

Second, the authentication delay occurs while an exchange ofAuthentication frames is made. The authentication includes two or fourconsecutive frames according to an authentication method used by the AP.Several wireless Network Interface Cards (NICs) attempt re-associationbefore the authentication. However, the attempted re-association causesan additional delay in the handover process.

Third, the re-association delay occurs while an exchange ofRe-association frames is made. If the Authentication phase issuccessfully achieved, the mobile station sends a Re-association Requestframe to the AP and receives a Re-association Response frame in responseto the request. This completes the handover. Meanwhile, the inclusion ofthe IAPP phase additionally required between the new AP and the otherAPs will further increase the re-association delay.

The mobile station suffers multiple delays in the process of performinghandover between APs in the conventional WLAN. This affects the qualityof service (QoS) and makes it impossible to perform fast handover.

Accordingly, there is a need for an improved system and method forproviding a re-association method for minimizing a service delay due tohandover in a WLAN mesh network.

SUMMARY OF THE INVENTION

An aspect of exemplary embodiments of the present invention is toaddress at least the above problems and/or disadvantages and to provideat least the advantages described below. Accordingly, an aspect ofexemplary embodiments of the present invention is to provide are-association method for minimizing a service delay due to handover ina WLAN mesh network.

It is another object of exemplary embodiments of the present inventionto provide a re-association method and system for minimizing anauthentication delay and a re-association delay due to handover in aWLAN mesh network.

According to one aspect of an exemplary embodiment of the presentinvention, a method and system for performing re-association due tohandover of a mobile node in a wireless local area network (WLAN) meshnetwork are provided. Authentication request information is transmittedalong with a mesh re-association request message for re-association of amesh network. A mesh re-association reply message is received includingan authentication reply to an authentication request corresponding tothe mesh re-association request message and a re-association phase isperformed according to the received mesh re-association reply message.

According to another aspect of an exemplary embodiment of the presentinvention, a method and system for performing re-association due tohandover by a new node in a wireless local area network (WLAN) meshnetwork are provided. A first mesh re-association request message isreceived. A second mesh re-association request message is generatedincluding moving information and authentication requests ofcorresponding nodes that transmitted the first mesh re-associationrequest message and the second mesh re-association request message istransmitted. A first mesh re-association reply message is received inreply to the second mesh re-association request message, a determinationis made as to whether there is an authentication reply to anauthentication request, and a second mesh re-association reply messageis generated including the authentication reply. The second meshre-association reply message is then transmitted to a corresponding nodethat transmitted the first mesh re-association request message.

According to another aspect of an exemplary embodiment of the presentinvention, a method and system for performing re-association due tohandover by an old node in a wireless local area network (WLAN) meshnetwork are provided. A mesh re-association request message is received,authentication is performed on a corresponding node in reply to anauthentication request included in the mesh re-association requestmessage, and a mesh re-association reply message is generated includingan authentication reply provided according to the authentication result,and the mesh re-association reply message is transmitted in reply to themesh re-association request message.

Other objects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other exemplary objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a signaling diagram schematically illustrating a handoverprocedure due to the movement of an STA in a general WLAN;

FIG. 2 is a diagram schematically illustrating data flow due to themovement of a mesh point (MP) in a WLAN mesh network according to anexemplary embodiment of the present invention;

FIG. 3 is a signaling diagram illustrating a Re-association phase due tothe movement of an MP in a WLAN mesh network according to an exemplaryembodiment of the present invention; and

FIG. 4 is a state diagram illustrating a Re-association phase due to themovement of an MP in a WLAN mesh network according to an exemplaryembodiment of the present invention.

Throughout the drawings, the same drawing reference numerals will beunderstood to refer to the same elements, features, and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The matters defined in the description such as a detailed constructionand elements are provided to assist in a comprehensive understanding ofthe embodiments of the invention. Accordingly, those of ordinary skillin the art will recognize that various changes and modifications of theembodiments described herein can be made without departing from thescope and spirit of the invention. Also, descriptions of well-knownfunctions and constructions are omitted for clarity and conciseness.

Exemplary embodiments of the present invention propose a re-associationsystem and method for a Wireless Local Area Network (WLAN) mesh network.In particular, an exemplary embodiment of the present invention providesan apparatus and method for simultaneously performing authenticationwhile performing re-association due to the movement of a mesh point in aWLAN mesh communication system. It will be assumed that the WLAN meshnetwork follows Institute of Electrical and Electronics Engineers (IEEE)802.11s standard.

Among IEEE 802.11 standards, the 802.11s standard does not requirecabling between the current access points (APs). The WLAN networkdefined in the IEEE 802.11s standard will be defined as a WLAN meshnetwork. As the IEEE 802.11s standard defines the connection betweennetworks, the WLAN mesh network can be easily installed at a lower costin areas where the installation of a conventional WLAN can be difficult.The WLAN mesh network can easily be installed in city environments suchas downtown areas.

The WLAN mesh network includes a plurality of nodes that exchange datawith each other. The nodes each include a plurality of terminals, orstations (STAs), a plurality of mesh points (MPs), and a plurality ofmesh access points (MAPs). The MP supports mesh service, and the MAP.The MAP is a special type of the MP which provides the mesh service andAP service.

Although exemplary embodiments of the present invention will bedescribed with reference to movement of the MP, an exemplary embodimentof the present invention can also be applied to every node capable ofperforming a Re-association phase.

FIG. 2 is a diagram schematically illustrating a data flow due to themovement of an MP in a WLAN mesh network according to an exemplaryembodiment of the present invention.

A description of FIG. 2 is made for cases in which an exemplaryembodiment of the present invention can be applied to a plurality of MPsand an MP1 211 transmits data to an MP6 229.

It will be assumed that the MP6 229 has previously received data servicevia an MP4 217 or an MP5 219 to transmit/receive data of the MP1 211. Asthe MP6 229 moves, it should perform handover. For example, the MP6 229should change the MP from which it receives the service, in order toreceive data of the MP1 211. In this process, the MP4 217 or the MP5 219that has previously provided the service to the MP6 229 becomes an oldMP, and an MP9 225 or an MP10 227 from which the MP6 229 will newlyreceive the service becomes a new MP.

The MP6 229 performs a Probe phase in which it asks each individual MPits opinion on the possibility of handover success possibility. Forexample, an inquiry is made regarding the possibility of MP changesuccess, in order to newly receive the data service from the new MP.

The Probe phase is similar in operation to the Probe phase described inthe Related Art section.

The MP9 225 or the MP10 227, selected according to their prioritiesdetermined in the Probe phase in the method described above, performs anAuthentication phase and a Re-association phase with the WLAN meshnetwork.

As a result, through the Probe phase, the Authentication phase and theRe-association phase, the MP6 229 can perform the service for the MP1211 via the new routes of ‘MP 1->MP 4->MP 2->MP 5->MP 7->MP 9->MP6’ and‘MP 1->MP 4->MP 2->MP 5->MP 7->MP 10->MP6’, instead of the old routes of‘MP 1->MP 4->MP 6’ and ‘MP 1->MP 4->MP 2->MP6’.

In order to simultaneously perform the Authentication phase and theRe-association phase, an exemplary embodiment of the present inventionincludes a phase of allowing the old MP to perform the Authenticationphase for the new MP. With reference to FIG. 2, a description will nowbe made of the Re-association phase according to an exemplary embodimentof the present invention.

FIG. 3 is a signaling diagram illustrating a Re-association phase due tothe movement of an MP in a WLAN mesh network according to an exemplaryembodiment of the present invention.

Referring to FIG. 3, a position-changed (such as, moved) MP6 310, a newMP (MP9 or MP10) 320, and an old MP (MP4 or MP5) 330 are shown.

The MP6 310 transmits data to at least one new MP 320 on a unicastbasis, without performing the Re-association phase with a plurality ofMPs. The MP6 310 transmits a Mesh Re-association Request message forperforming the Re-association phase in step 311. The Mesh Re-associationRequest message includes an Authentication request and an Old MP list.

Upon receiving the Mesh Re-association Request message, the new MP 320forwards the Mesh Re-association Request message to the old MP 330 basedon the Old MP list included in step 313. In this case, the new MP 320provides information on the moved MP6 310 to the old MP 330 along withthe Mesh Re-association Request message. The new MP 320 also sends arequest for establishment of a route from the new MP, such as, MP9 orMP10, of the MP6 310 to the old MP 330.

The old MP 330 which receives the Mesh Re-association Request messagetransmitted by the new MP 320, performs an authentication correspondingto the Authentication request of the MP6 310 and performs a routingtable update for data transmission, such as, packet transmission, to theMP6 310.

The old MP 330 manages a re-association table for the MP6 310. There-association table refers to a table including a list generated sothat MPs exchange Re-association Request/Reply messages with each other,and register counterpart information to facilitate future communication.

Therefore, after receiving the re-association table of the MP6 310through the Mesh Re-association Request message, the old MP 330 managesan MP6 entry, such as, information on the MP6 310, in a postponementstate for a predetermined time. This is done without immediatelydiscarding the MP6 entry. The re-association table is managed in thepostponement state for a predetermined time without immediatelydiscarding the MP6 entry so that a packet loss can be prevented bystoring information given until completion of the re-association becausethe packets to be transmitted to the MP6 310 are transmitted to the oldMP 330 until the completion of the re-association.

After receiving the Mesh Re-association Request message, the old MP 330establishes a route up to the MP6 310 that passes through the new MP320, such as, MP9 or MP10, using a routing table for the MP6 310.

The old MP 330 manages the routing table update and the re-associationtable, and transmits a Mesh Re-association Reply message to the new MP320 in response to the Mesh Re-association Request message in step 315.

The new MP 320 determines whether the MP6 310 has passed theauthentication, using Mesh Re-association Reply message, and forwardsthe Mesh Re-association Reply message to the MP6 310 according to thedetermination result in step 317.

After the Re-association phase, the MP6 310 receives data through theold MP 330, such as, the MP5, in step 319.

Advantageously, the MPs can request the Authentication phase and theRe-association phase through the Mesh Re-association Request message andcan also simultaneously perform the Authentication phase and theRe-association phase using the Mesh Re-association Request message.

FIG. 4 is a state diagram illustrating a Re-association phase due to themovement of an MP in a WLAN mesh network according to an exemplaryembodiment of the present invention.

Referring to FIG. 4, step 411 represents State 1 in which a moving MP isunauthenticated and unassociated. Step 413 represents State 2 in whichthe moving MP is authenticated but is unassociated. Step 415 representsState 3 in which the moving MP is authenticated and associated. Step 417represents State 4 in which the moving MP is mesh-unauthenticated andmesh-unassociated.

The conventional re-association is achieved in order of ‘State 1->State2->State 3’ for the authentication and the re-association. If the movingMP passes the authentication in State 1, it transitions to State 2, andif the moving MP succeeds in both the authentication and there-association in State 2, it transitions to State 3. However, if themoving MP fails in the re-association in State 3, it transitions toState 2, and if the moving MP fails in the authentication in State 2, ittransitions to State 1.

However, an exemplary embodiment of the present invention proposes State4 to perform a Mesh Re-association phase including the Authenticationphase which makes it possible to perform service through simplifiedstate transition. In an exemplary embodiment of the present invention,the states are reduced in number to two states of ‘State 4->State 3’,and the authentication is performed by the old MP instead of the new MP.As a result, it is possible to perform re-association through aplurality of MPs and the above phases in the WLAN mesh network, usingthe existing method.

As illustrated in FIG. 4, if the moving MP succeeds in theauthentication and the re-association in State 4, it transitions toState 3. However, if the moving MP fails in the authentication in State4, it transitions to State 1.

As can be understood from the foregoing description, in the WLAN meshnetwork, an exemplary embodiment of the present invention simultaneouslyperforms the Authentication phase during re-association, therebyminimizing a possible handover delay. In addition, an exemplaryembodiment of the present invention can minimize a service delay andoverhead caused by the movement of a node, especially an MP in the WLANmesh network.

While the present invention has been shown and described with referenceto certain exemplary embodiment thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for performing re-association accordingto handover of a mobile node, by an old node in a wireless mesh network,the method comprising: receiving, from a new node, a mesh re-associationrequest message, the mesh re-association request message comprisingmoving information of the mobile node; and establishing, in response tothe mesh re-association request message, a route between the old node,one or more intermediate mesh nodes between the old node and the newnode, and the new node, based on the moving information received fromthe new node.
 2. The method of claim 1, wherein the mesh re-associationrequest message further comprises authentication request information,which the new node receives from the mobile node, for the authenticationof the mobile node.
 3. The method of claim 2, further comprising:authenticating the mobile node based on the authentication requestinformation; generating a mesh re-association reply message comprisingauthentication reply information according to a result of theauthenticating; and transmitting, to the new node, the meshre-association reply message in reply to the mesh re-association requestmessage.
 4. The method of claim 1, further comprising: transmitting datapackets whose destination is the mobile node to the mobile node throughthe route between the old node, the one or more intermediate mesh nodesand the new node.
 5. The method of claim 1, further comprising:maintaining a corresponding entry of a re-association table for themobile node for a predetermined time after receiving the meshre-association request message; and discarding the corresponding entryafter the predetermined time.
 6. The method of claim 1, the establishinga route comprises: performing re-association to establish the routebased on a re-association table of the mobile node managed by the oldnode, the re-association table comprising information on nodes that areable to communicate with the old node.
 7. The method of claim 1, whereinthe old node is a node from which the mobile node has previouslyreceived data, and the new node is at least one node from which themobile node desires to receive data.
 8. A method for performingre-association according to handover of a mobile node, by an new node ina wireless mesh network, the method comprising: receiving, from themobile node, a first mesh re-association request message, the first meshre-association request message comprising moving information of themobile node; transmitting, to an old node, a second mesh re-associationrequest message, the second mesh re-association request messagecomprising the moving information of the mobile node; receiving datapackets whose destination is the mobile node through a route between theold node, one or more intermediate mesh nodes between the old node andthe new node, and the new node, the route established based on themoving information; and transmitting the data packets to the mobilenode.
 9. The method of claim 8, further comprising: receiving, from theold node, a first mesh re-association reply message in reply to thesecond mesh re-association request message; and transmitting, to themobile node, a second mesh re-association reply message corresponding tothe first mesh re-association reply message.
 10. The method of claim 9,wherein the first mesh re-association request message further comprisesauthentication request information for the authentication of the mobilenode, and the second mesh re-association request message furthercomprises the authentication request information.
 11. The method ofclaim 10, wherein the first mesh re-association reply message comprisesauthentication reply information according to a result of authenticatingof the mobile node by the old node, and the second mesh re-associationreply message comprises the authentication reply information.
 12. Themethod of claim 8, wherein the first mesh re-association request messagefurther comprises an old node list, the old node list comprisinginformation on the old node.
 13. A method for performing re-associationaccording to handover by a mobile node in a wireless mesh network, themethod comprising: transmitting, to a new node adjacent to the mobilenode, a mesh re-association request message for re-association of thewireless mesh network to establish a route among the mobile node, thenew node, and an old node; and receiving, from the new node, a meshre-association reply message in response to the mesh re-associationrequest message, wherein the route is established between the old node,one or more intermediate mesh nodes between the old node and the newnode, and the new node.
 14. The method of claim 13, wherein the meshre-association request message comprises moving information of themobile node and authentication request information for theauthentication of the mobile node.
 15. The method of claim 14, whereinthe mesh re-association reply message comprises authentication replyinformation according to a result of authenticating of the mobile nodeby the old node.
 16. The method of claim 13, wherein the meshre-association request message comprises an old node list, the old nodelist comprising information on the old node, which is a node from whichthe mobile node has previously received data.
 17. The method of claim13, further comprising: receiving data packets whose destination is themobile node from the new node through the route between the old node,the one or more intermediate mesh nodes and the new node.
 18. The methodof claim 13, wherein the mesh re-association request message istransmitted to the new node on a unicast basis.